CELL-WALL ULTRASTRUCTURE IN RESTING-SPORES OF POLYMYXA-BETAE KESKIN (PLASMODIOPHORACEAE)

The structure of the resting spore wall of Polymyxa betae KESKIN was i nvestigated by cytochemical reactions at TEM and enzymatic treatments. Of the five layers making up the mature cell wall, the first two are intimately interconnected, the third is rather electron-transparent an d fibrous, while PATAg reveals the fourth to be thin and rich in polys accharidic materials. The fifth, innermost layer varies in appearance according to the various stages of maturation and to the area examined . During the maturation of the resting spore it forms in the upper are a a discoidal area which disappears before germination. The wall, on t he whole, is resistant to enzymatic treatment with pronase, lipase and phospholipase, and is destroyed by lysozyme. Our results provide evid ence for a progressive modification of the upper area of the cell wall from a simpler to a more complex structure during the maturation of t he spore and in relation to germination. Cytochemical tests and enzyma tic studies yield no reliable evidence on the chemical composition of the wall, with the exception of the fourth layer, where the polysaccha ridic components are localised.